Gas turbine engines, and other turbomachines, include multiple sections, such as a fan section, a compressor section, a combustor section, a turbine section, and an exhaust section. Air moves into the engine through the fan section. Blade arrays in the compressor section rotate to compress the air, which is then mixed with fuel and combusted in the combustor section. The products of combustion are expanded to rotatably drive blade arrays in the turbine section. The turbine section drives rotation of the fan section and compressor section.
Turbomachines typically include arrangements of blade outer air seals circumferentially disposed about the blade arrays. During operation of the turbomachine, the tips of the blades rotate relative to the blade outer air seals. As known, improving and maintaining the sealing relationship between the blades and the blade outer air seals can desirably enhance performance of the turbomachine.
In some prior art designs, pressurized air or springs force the blade outer air seals radially inward to a fixed position. The pressurized air holds the blade outer air seals in the fixed position against hard stops as the blade arrays rotate relative to the blade outer air seals. The hard stops are generally not perfectly round or centered, whereas the blade arrays are round and centered. The radial variation in the hard stops causes the radial position of the blade outer air seals to vary, which means that the clearance between a tip of a given blade and the blade outer air seals varies as the blade array is rotated. Also, in these designs, the blade moves radially relative to the blade outer air seals during operation. Clearance between the tip of the give blade and the blade outer air seals varies for at least this reason as well. The blade outer air seal remains stationary relative to the blade because the blade outer air seals are forced against the hard stops.